There is a gotcha with qemu_log() usage in a threaded process.
If fragments of a log message are output via qemu_log() it is
possible for messages from two threads to get mixed up. To
prevent this qemu_log_trylock() should be used, along with
fprintf(f) calls.
This is a subtle problem that needs to be explained in the
API docs to ensure correct usage.
In the Rust code, the log_mask_ln method which is conceptually
equivalent to the C qemu_log() call will unconditionally append
a newline so must only ever be used for complete log messages.
Reported-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
e43c84813f